The
first camera obscura that was small enough for practical use as a portable
drawing aid was built by Johann
Zahn in 1685.At that time there was no way to preserve the images
produced by such cameras except by manually tracing them. However, it had long
been known that various substances were bleached or darkened or otherwise
changed by exposure to light. Seeing the magical miniature pictures that light
temporarily "painted" on the screen of a small camera obscura
inspired several experimenters to search for some way of automatically making
highly detailed permanent copies of them by means of some such substance.
Early
photographic cameras were usually in the form of a pair of nested boxes, the
end of one carrying the lens and the end of the other carrying a
removable ground glass focusing screen. By sliding them closer
together or farther apart, objects at various distances could be brought to the
sharpest focus as desired. After a satisfactory image had been focused on the
screen, the lens was covered and the screen was replaced with the
light-sensitive material. The lens was then uncovered and the exposure
continued for the required time, which for early experimental materials could
be several hours or even days. The first permanent photograph of a
camera image was made in 1826 by Joseph
Nicéphore Niépce using a sliding wooden box camera made by Charles and Vincent Chevalier in
Paris.
Similar
cameras were used for exposing the silver-surfaced copper Daguerreotype plates, commercially introduced in
1839, which were the first practical photographic medium. The collodion wet
plate process that gradually replaced the Daguerreotype during the 1850s
required photographers to coat and sensitize thin glass or iron plates shortly
before use and expose them in the camera while still wet. Early wet plate
cameras were very simple and little different from Daguerreotype cameras, but more sophisticated designs eventually
appeared. The Dubroni of 1864 allowed the sensitizing and developing of
the plates to be carried out inside the camera itself rather than in a
separate darkroom. Other cameras were fitted with multiple lenses for
photographing several small portraits on a single larger plate, useful when
making cartes de visite. It was
during the wet plate era that the use of bellows for focusing became
widespread, making the bulkier and less easily adjusted nested box design
obsolete.
For
many years, exposure times were long enough that the photographer simply
removed the lens cap, counted off the number of seconds (or minutes)
estimated to be required by the lighting conditions, then replaced the cap. As
more sensitive photographic materials became available, cameras began to
incorporate mechanical shutter mechanisms that allowed very short and
accurately timed exposures to be made.
The
electronic video camera tube was invented in the 1920s, starting a
line of development that eventually resulted in digital cameras, which
largely supplanted film cameras after the turn of the 21st century.
Johann
Zahn
Johannes
C. A. Zahn was the son of Eschenbach teacher and cantor Johannes Zahn. Between 1832 and 1837 he attended the Nuremberg high
school, and studied afterwards in Berlin to obtain his degree in theology in
1841. After attending the Predigerseminar in Munich, he
became a house teacher for the residence of Gustav Schulze, a prominent merchant.
In
1847 he was named teacher and prefect of the Royal Schullehrer Seminar in Altdorf bei Nürnberg, and became its head
in 1854.
Johannes
Zahn dedicated himself particularly to the recovery and critical revision of
melodies and hymns developed during and after the Reformation, which he
started publishing in 1889, in Gütersloh.
The classification system he developed is still used by hymnologists worldwide,
in the form Zahn, where the number represents the location of the melody
or hymn in Zahn's anthology
Zahn
also contributed articles to journals like Siona, Hymnologie, and Euterpe.
Zahn
also composed hymns, and is known for writing the original melody Dein
König kommt in niedern Hüllen, number 14 in the Evangelisches Gesangbuch still
in use in Lutheran German churches.
Nicéphore
Niépce March 7,
1765 – July 5, 1833) was a French inventor, most noted as one
of the inventors of photography and a pioneer in the field. He is most noted for producing
the world's first known photograph in 1825. Among
Niépce's other inventions was the Pyréolophore, the world's first
'internal combustion engine', which he
conceived, created, and developed with his older brother Claude, finally receiving
a patent on July 20, 1807 from the Emperor Napoleon
Bonaparte, after successfully powering a boat upstream on the river Saône.
Reference:
http://en.wikipedia.org
